Recent years have shown a significant increase of the speed of interfaces for an interconnection between information devices. With the increase of the speed of the connection provided by interfaces, “transmission parameters” for transmission signals are often adjusted between devices. An example of the “transmission parameters” is an emphasis value which indicates the degree of emphasis on the amplitude of a transmission signal or a transmission waveform in a high-frequency band. Adjustment of the transmission parameters is important especially for ensuring transmission quality in the case of using a high-speed interface. However, it is often the case that adjustment of transmission parameters is performed only at the time of establishing a link between information devices without performing adjustment thereafter until the link is disconnected, instead of performing the adjustment constantly.
Japanese Patent Application Laid-open Publication No. 2011-41109 (referred to as “Patent Literature 1” below) discloses that multiple values are prepared for each transmission parameter in advance. For example, in the technique of Patent Literature 1, multiple values are prepared for each transmission parameter so as to correspond to the respective operation frequencies to be used by an interface. In the technique of Patent Literature 1, when the interface operates in a power-saving mode, a value of each transmission parameter corresponding to the operation frequency of the power-saving mode is selected. By contrast, when the interface operates in a high-speed mode, a value of each transmission parameter corresponding to an operation frequency of the high-speed mode is selected. In the technique of Patent Literature 1, the value of transmission parameter selected for each operation frequency is used by the interface.
As described above, in the technique of Patent Literature 1, values are prepared in advance for each transmission parameter so as to correspond to the respective operation modes of the interface. This allows the technique of Patent Literature 1 to eliminate the need for time to adjust transmission parameters at the time of changing between the operation modes, and to use of the optimal value of each transmission parameter.